Inorganic honeycomb manufacture is known, for example, from U.S. Pat. Nos. 3,122,184 (Hollenbach) and 3,790,654 (Bagley). Also known are procedures for the application of surfacing or plugging materials to such honeycombs, for purposes such as the sealing or selective blocking of surface pores or channels in the honeycomb structure to obtain a desired fluid flow pattern therein. U.S. Pat. No. 4,199,387, for example, describes a sealing method wherein a cement is spread on the outside surface of a honeycomb body.
Currently in large-scale commercial use is the extrusion of ceramic and metal honeycombs for fluid heating, catalytic treating, and/or fluid filtration applications. Examples of products produced by these methods are porous ceramic honeycomb bodies specially adapted for use as exhaust gas filters in diesel engine exhaust systems (referred to as DPF's). U.S. Pat. Nos. 4,417,908 (Pitcher) and 4,329,162 (Pitcher) disclose examples of these DPF products.
In one approach to the manufacture of honeycomb substrates for fluid filtration applications, substrate honeycombs of oversize dimensions are first extruded from batches of particulate ceramic or metal material, and then reshaped after drying to a size and shape appropriate for their intended use. This resizing, also termed contouring, is used to prepare the substrates for the application of surfacing or skin layers of ceramic material, by finalizing the shape and/or dimensions of the extruded body as needed for encasing or "canning" the body in a suitable durable container for later use.
Oversize extrusion followed by contouring can be economically attractive, since by that means a variety of honeycomb products of a selected cell size, shape and density can be produced from the extruder output of a single extrusion production line. However, such production is presently disadvantaged to the extent that contouring must be carried out by band-sawing and or wet-sanding of the dried extruded honeycomb shapes. Sawing is not economical because of problems relating to low blade life, and in addition has had application to the production of substrates of round cross-section only. Sanding is disadvantageous because it is time consuming and labor intensive, requires a post-drying operation, and produces inconsistent results.
It is therefore an object of the present invention to provide a new contouring process applicable to the production of inorganic honeycomb substrates for a variety of applications.
It is a further object of the invention to provide a process for honeycomb substrate manufacture which produces a more uniform product at lower cost and in a shorter time.
It is a further object of the invention to provide apparatus for the contouring of extruded honeycomb substrates which provides rapid contouring of both dried and fired ceramic honeycomb bodies on a consistent and repeatable basis.
Other objects and advantages of the invention will become apparent from the following description thereof.